Interaction of Methane with Single-Walled Carbon Nanotubes： Role of Defects,Curvature and Nanotubes Type

We investigate the interaction of single-walled carbon nanotubes （SWCNTs） and methane molecule from the first principles. Adsorption energies are calculated, and methane affinities for the typical semiconducting and metallic nanotubes are compared. We also discuss role of the structural defects and nanotube curvature on the adsorption capability of the SWCNTs. We could observe larger adsorption energies for the metallic CNTs in comparison with the semiconducting CNTs. The obtained results for the zig zag nanotubes with various diameters reveal that the adsorption energy is higher for nanotubes with larger diameters. For defected tubes the adsorption energies are calculated for various configurations such as methane molecule approaching to the defect sites pentagon, hexagon, and heptagon in the tube surface. The results show that the introduce defects have an important contribution to the adsorption mechanism of the methane on SWNTs.     

Electronics and Structural Properties of Single-Walled Carbon Nanotubes Interacting with a Glucose Molecule: ab initio Calculations

The adsorption of glucose molecule on single-walled carbon nanotubes(SWCNTs)is investigated by density functional theory calculations.Adsorption energies and equilibrium distances are evaluated,and glucose binding to the typical semiconducting and metallic nanotubes with various diameters and chirality are compared.We also investigated the role of the structural defects on the adsorption capability of the SWCNTs.We could observe larger adsorption energies for the larger diameters semiconducting CNTs,while the story is paradoxical for the metallic CNTs.The obtained results reveal that the adsorption energy is significantly higher for nanotubes with higher chiral angles.Finally,the adsorption energies are calculated for defected nanotubes for various configurations such as glucose molecule approaching to the pentagon,hexagon,and heptagon sites in the tube surface.We find that the respected defects have a minor contribution to the adsorption mechanism of the glucose on SWNTs.The calculation of electron transfers and the density of states supports that the electronic properties of SWCNTs do not change significantly after the gluycose molecular adsorption.Consequently,one can predict that presence of glucose would neither modify the electronic structure of the SWCNTs nor direct to a change in the conductivity of the intrinsic nanotubes.     

修饰银电极上单壁碳纳米管的表面增强拉曼散射

本文采用修饰了银纳米颗粒的银电极作为基底,获得了高质量的单壁碳纳米管(SWCNTs)的表面增强拉曼散射(SERS)光谱。在1100~1500 cm-1范围内观测到了一组表征SWCNTs结构的新峰。修饰在银电极上的银纳米颗粒不仅可以保证SWCNTs在这一体系中吸附的紧密性,而且通过变面等离子体共振起到了电磁放大的作用。通过对银纳米颗粒修饰银电极表面SWCNTs的SERS光谱及其随电位变化的SERS光谱的研究,我们可以研究这一过程中的SERS机制。理论和实验结果表明,银纳米颗粒修饰银电极上单壁碳纳米管的SERS很有潜力成为一种检测单壁碳纳米管合成质量的新方法。     

Structures and Vibrational Spectra of the Hydrogen-Bonded Complexes Between Nitrous Acid and Acetone: Ab Initio and DFT Studies

ABSTRACT

The structures, stability, and vibrational spectra of the binary complexes formed between acetone and nitrous (trans and cis) acid have been investigated using ab initio calculations at the SCF and MP2 levels and B3LYP calculations with 6-311++G(d,p) basis set. Full geometry optimization was made for the complexes studied. It was established that the complex (CH₃)₂CO···HONO-trans is more stable than the complex (CH₃)₂CO···HONO-cis by 0.5–0.8 kcal·mol^?1. The accuracy of the calculations has been estimated by comparison between the predicted values of the vibrational characteristics (vibrational frequencies and infrared intensities) and the available experimental data. It was established, that the methods, used in this study are well adapted to the problem under examination. The predicted values with the B3LYP/6-311++G(d,p) calculations are very near to the results, obtained with MP2/6-311++G(d,p). The calculated frequency shift Δν(O[sbnd]H) for the complex (CH₃)₂CO···HONO-trans (1A) is larger than for the complex (CH₃)₂CO···HONO-cis (1B). In the same time the intensity of this vibration increases dramatically upon hydrogen bonding. The calculated increase for the complex 1A is up to 15 times and for the complex 1B is up to 30 times. The changes in the vibrational characteristics (vibrational frequencies and infrared intensities) of (CH₃)₂CO upon the complexation are more insignificant than the changes in the vibrational characteristics of HONO-trans and HONO-cis.     

高压下TiN的结构转变、弹性和热力学性质的第一性原理计算

 利用基于密度泛函的第一性原理,计算了高压下TiN的结构转变、弹性和热力学性质。计算结果表明：在压力作用下,TiN经历了从NaCl型结构到CsCl型结构的转变,转变压力为348 GPa;TiN的弹性系数随着压力的增加呈线性增加规律。此外,还给出了德拜温度和热容量这两个重要热力学量与温度和（或）压力的依赖关系。     

碳纳米管/寡聚胸腺嘧啶复合体系与汞离子作用的光谱研究

利用寡聚胸腺嘧啶核苷酸(PolyT)与碳纳米管(CNTs)之间的自发非共价修饰作用形成稳定的CNTs/PolyT纳米复合体系,采用共振光散射(RLS)和紫外-可见吸收光谱考察了该复合体系与汞离子的相互作用.实验结果表明,水相中单链PolyT能与CNTs形成稳定而均匀的分散体系,而单链Po1yT极易捕获汞离子生成特异性的...     

浓硝酸处理碳纳米管对4-硝基苯酚的吸附性能研究

本文采用浓硝酸氧化法来改性多壁碳纳米管,用Raman光谱、SEM和分光光度计对改性前后的多壁碳纳米管对4-硝基苯酚溶液的吸附能力进行了比较研究。Raman光谱和SEM分析表明浓硝酸处理使碳纳米管端口打开,管变短,并且在表面引入了羟基、羧基等酸性官能团。采用分光光度计测定溶液浓度,计算出浓硝酸处理前后多壁碳纳米管对不同浓度4-硝基苯酚的吸附效率,实验结果表明经浓硝酸处理后的多壁碳纳米管的吸附效率有较大的提高。     

光谱法研究水溶性羧基化碳纳米管与人血清白蛋白的相互作用

纳米材料与蛋白质等生物大分子的相互作用是纳米材料生物效应和安全性研究的重要基础。本实验利用荧光光谱、同步荧光光谱、圆二色谱(CD)等方法研究了四种结构特性不同的水溶性羧基化碳纳米管(long-SWCNTs-COOH,short-SWCNTs-COOH,DWCNTs-COOH,MWCNTs-COOH)与人血清白蛋白(human serum albumin, HSA)的相互作用。实验结果显示：四种水溶性羧基碳纳米管均能猝灭HSA的内源荧光,但猝灭能力有所不同,相同浓度下不同水溶性羧基化碳纳米管对HSA的荧光猝灭作用遵循如下规律：DWCNTs-COOH＜MWCNTs-COOH＜long-SWCTs-COOH＜short-SWCNTs-COOH;四种碳纳米管对HSA的同步荧光光谱影响表明,MWCNTs-COOH的作用位点更靠近色氨酸(Trp)残基,而DWCNTs-COOH的作用位点更靠近酪氨酸(Tyr)残基,而long-SWCNTs-COOH和short-SWCNTs-COOH对两种氨基酸残基的作用无明显差别;在碳纳米管作用下,HSA 的圆二色谱有微弱的变化,且与α-螺旋、β-折叠含量变化基本一致。结果表明,不同碳纳米管对HSA的荧光猝灭能力与它们的结构特性有关,两者作用过程中HSA构象基本不变,二级结构有微小变化,但无明显的剂量-效应关系。根据实验结果对可能的作用机制进行了讨论。     

磁场对单壁碳纳米管电子结构和光学性质的影响

我们采用半经验的模型、用单激发组态相互作用方法计算并讨论了外加轴向磁场对单壁碳纳米管电子结构和光学性质的影响。由于电子电子间相互作用的影响,磁场导致碳纳米管吸收峰能级分裂与磁场不成正比。该结果与简单的能带理论所给出的结果在低磁场情况下有本质的区别,并与实验结果有更高的符合度。该研究进一步证明了电子电子间相互作用以及激子在决定碳纳米管电子结构和光学性质中的重要作用。     

磁场对单壁碳纳米管电子结构和光学性质的影响

采用半经验的模型、用单激发组态相互作用方法计算并讨论了外加轴向磁场对单壁碳纳米管电子结构和光学性质的影响。由于电子电子间相互作用的影响,磁场导致碳纳米管吸收峰能级分裂与磁场不成正比。该结果与简单的能带理论所给出的结果在低磁场情况下有本质的区别,并与实验结果有更高的符合度。该研究进一步证明了电子电子间相互作用以及激子在决定碳纳米管电子结构和光学性质中的重要作用。     

NH自由基与臭氧反应机理的理论研究

用量子化学从头计算方法,在HF／6－31＋＋G**水平研究了臭氧与NH三线态活性自由基反应的微观机理,优化得到反应物、过渡态、中间体和产物的几何构型。用MP2／6－31＋＋G**／／HF6－31＋＋G**方法计算能量,同时进行零点能校正。研究结果表明： NH三线态活性自由基与O3反应首先成稳定中间体NHO3,然后中裂解生成HNO和O2。     

O3与O3分子间相互作用的理论研究

采用从头算方法,在B3LYP水平下对O3分子单体及其二聚体进行了几何结构优化,得到四种O3分子二聚体的稳定构型,并经MP2法、均衡法(Massage)分别校正了电子相关和基组叠加误差(BSSE),通过对分子中原子间的最短距离,分子间质心距离与各构型相互作用能的关系进行了分析、比较,得到了最稳定的构型,其对应的O3分子二聚体相互作用能为:-8.788 kJ/mol.     

Theoretical stability,thin film synthesis and transport properties of the Mon +1GaCn MAX phase

The phase stability of Mo_{n +1}GaC_n has been investigated using ab‐initio calculations. The results indicate stability for the Mo₂GaC phase only, with a formation enthalpy of –0.4 meV per atom. Subsequent thin film synthesis of Mo₂GaC was performed through magnetron sputtering from elemental targets onto Al₂O₃ [0001], 6H‐SiC [0001] and MgO [111] substrates within the temperature range of 500 °C and 750 °C. High structural quality films were obtained for synthesis on MgO [111] substrates at 590 ºC. Evaluation of transport properties showed a superconducting behavior with a critical temperature of approximately 7 K, reducing upon the application of an external magnetic field. The results point towards the first superconducting MAX phase in thin film form. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

功能纳米结构可控生长的新途径：非模板选择性自组装

文章介绍了一种非模板选择性自组装纳米结构的方法.从实验和理论上研究了两种有机分子在Ag单晶不同表面上的吸附行为,发现在Ag（775）基底上PTCDA分子会完全吸附在（111）台阶面上,而DMe-DCNQI分子则完全吸附在（221）台阶面上.该研究还阐明了PTCDA分子与基底原子之间的相互作用机制,提出了PTCDA与基底之间的相互作用是通过分子末端官能团的氧原子实现的,中心的π共轭区域与基底相排斥,理论模拟得到的氧原子的NIXSW相干长度以及碳原子的近边X射线吸收谱与实验结果符合得较好.     

Effects of Radius and Orientation of Single-Walled Carbon Nanotubes on Their Nonlinear Tensile Deformation Behaviour

By capturing the atomic information and reflecting the behaviour governed by a nonlinear potential function, an analytical molecular mechanics approach is applied to establish the constitutive relation for single-walled carbon nanotubes （SWCNTs）. The nonlinear tensile deformation curves of zigzag and armchair nanotubes with different radii are predicted, and the elastic properties of these SWCNTs are obtained. A conclusion is made that the nanotube radius has little effect on the mechanical behaviour of SWCNTs subject to simple tension, while the nanotube orientation has larger influence.     

Theoretical study of ZnO adsorption and bonding on Al_2O_3(0001) surface

Sapphire (α-Al2O3) and silicon (Si) are widely applied as the substrates of the highquality ZnO thin films prepared by pulse laser deposition (PLD) and molecule beamepitaxy (MBE) technology. The adhesion, diffusivity, and bonding of the particles on thesubstrates play a significant role in the forming and initial growing of nucleation for filmgrowth, and directly influence the quality of the entire thin films[1]. No sufficient studiesand experiments are available on the surface atomic str…     

Acetone Adsorption on Pristine and Pt-doped Graphene: A First-Principles vdW-DF Study

Using van der Waals corrected density functional theory (vdW-DF) method we have investigated the adsorption of acetone molecule on pristine and Pt-doped graphene. Several active sites for both the interacting systems have been considered in the adsorption process including full geometry optimization. We have analyzed the structural and electrical properties of energetically favorable configurations. The results show that adsorption of acetone molecule on the Pt-doped graphene is energetically preferable. The binding energy and bonding distance are determined to be -5.277 eV and 2.206 Å, respectively, accompanying with charge transfer of 1.11 e. Furthermore, the Pt-O bond is rather significantly elongated when acetone is adsorbed on Pt-doped graphene. Compared to pristine graphene, the Pt-doped graphene has stronger interaction with the acetone and may provide more sensitive signal for a single acetone molecule. Meanwhile, practically, the band gap of Pt-doped graphene would become reduced after acetone adsorption. Consequently, our first-principles study presents evidence for a coherent benchmark for the applicability of Pt-doped graphene for acetone adsorption and detection.     

Spectroscopic Studies on Pure and Histidine-Functionalized Multiwalled Carbon Nanotubes

Electron paramagnetic resonance, Fourier transform infrared, and ultraviolet-visible studies were carried out for pure and histidine-functionalized multiwalled carbon nanotubes. Electron paramagnetic resonance absorption spectral data were found to be the best fit for the Gaussian lineshape. The g-values indicate the presence of magnetic impurities in the samples and the interaction between the localized electrons and delocalized electrons in the nanotubes trapped at defects or magnetic ion sites. The electron spin concentration decreases with increasing concentration of histidine, which implies that the unpaired electrons undergo a reduction process in the histidine-functionalized multiwalled carbon nanotubes. Fourier transform infrared study confirms the presence of functional groups in pure and histidine-functionalized multiwalled carbon nanotubes. Ultraviolet-visible study reveals the formation of a charge transfer complex in histidine-functionalized multiwalled carbon nanotubes.     

Experimental and Theoretical Studies on the Interaction between Isonicotinic Acid Molecules and Silver Nanoclusters

The present paper describes the studies on the adsorption behavior and charge transfer from isonicotinic acid to silver nanoparticles with experiment and theory. Compared with UV–Visible adsorption spectrum, the adsorption spectrum of Ih-Ag₁₃ cluster was quite good agreed with that of silver colloidal nanoparticle. So that one Ag₁₃ cluster as a substrate was used to simulate Raman frequencies of the adsorption configuration. Here, it is demonstrated the calculated Raman spectra are in good agreement with experimental results. The analysis of Mulliken charge was obtained by density functional theory, which indicated the charge characteristics of Ag₁₃ nanoparticle. Once isonicotinic acid molecules were adsorbed on sliver clusters, the charges transfer from isonicotinic acid to silver clusters, so that the surface charges of silver clusters are uneven.     

Theoretical investigations on structural, elastic and electronic properties of thallium halides

Theoretical investigations on structural, elastic and electronic properties, viz. ground state lattice parameter, elastic moduli and density of states, of thallium halides (viz. TlCl and TlBr) have been made using the full potential linearized augmented plane wave method within the generalized gradient approximation (GGA). The ground state lattice parameter and bulk modulus and its pressure derivative have been obtained using optimization method. Young's modulus, shear modulus, Poisson ratio, sound velocities for longitudinal and shear waves, Debye average velocity, Debye temperature and Grüneisen parameter have also been calculated for these compounds. Calculated structural, elastic and other parameters are in good agreement with the available data.